Peripheral diamond grinding wheel



NOV- 9, 1943 E. VAN DER PYL 2,334,048'

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Patented Nov. 9, 1943 UNITED STATES PATENT OFFICE Application December 1, 1941, Serial No. 421,152

13 Claims.

The invention relates to diamond grinding wheels, particularly of the metal bonded type. 'I'his application is a continuation in part of my copendng application Serial No. 338,870 filed June 5, 1940. This application also discloses and contains certain subject matter common to it and .my copending application Serial No. 421,151 led concurrently herewith which discloses another species of my invention, and it is in my present application that such subject matter common to all species is generically claimed.

One object of the invention is to provide a diamond grinding wheel bonded with metal bond with a resinoid center or support. Another object of the invention is to provide an improved construction permitting a tight union between the metal bonded ring-like grinding portion and the resinoid center or support. Another object of the invention is to provide a grinding wheel of light weight which readily dissipates heat. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts, and in the several steps and relation and order of each of said steps t one or more of the others thereof, all as will be illustratively described herein and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing, in which two of many possible embodiments of the mechanical features of this invention are shown, and in which every view is an axial sectional view,

Figure 1 shows a mold filled with metal powder before the first pressing operation;

Figure 2 shows a metal ring produced by the pressing operation of Figure l;

Figure 3 shows the mold of Figure 1. containing the metal ring of Figure 2 after it has been reduced in diameter, and containing also loose diamonds and metal powder to form the diamond abrasive portion;

Figure 4 shows another mold containing the metal ring with the metal bonded diamond portion produced by the pressing operation illustrated in Figure 3 after the ring has been sintered and machined, and also containing a loosely pressed disk of, for example A stage resin;

Figure 5 shows the completed article; and

Figure 6 illustrates a modification.

I provide a quantity of diamond fragments of small size, such as abrasive grit sizes 80 to 400 where the wheel is to contain diamonds as the abrasive, and where the abrasive is to be metalbonded, I also provide a quantity of metal powder. Within the scope of this invention, any

.other abrasive such as fused alumina, emery,

corundum, silicon carbide, 'boron carbide, tungsten carbide or titanium carbide may be used. Also, within the scope of this invention, any metal bond may be employed although I prefer to use one of the bonds of my own prior Patent Reissue No. 21,165, preferably copper and tin, using about 20% of tin and the remainder of copper. Other combinations mentioned in this reissue patent are copper-nickel, copper-aluminum, copper-manganese, and copper-beryllium. Other metal bonds which have been suggested, such as iron, aluminum-silicon, aluminum-copper, and aluminumiron, might be employed. So also in certain cases I might use such bonds as cobalt or nickel. I may also use any 0f the bonds described in or within the scope of my Patent No. 2,238,351, such as 25% each of copper, tin, iron and nickel. With such materials I then proceed preferably as follows:

Referring now to Figure 1, I provide a mold comprising an outer mold ring or band I0, an inner mold ring II, an annular bottom plate I2, and an annular top pressing plate I3. I fill the annular space between these four parts with the desired metal powder or mixture of metal powders I4. I then put the mold in a hydraulic press and press with a pressure of the order of five to ten (short) tons to the square inch. I then strip the mold vand remove the pressed article and place it in a suitable chuck of a lathe and, where it is to be provided with an abrasive portion on its outer cylindrical periphery, I then remove metal on the periphery to reduce the diameter of the ring. The amount of metal taken off should slightly exceed the ultimate radial thickness of the abrasive portion of the final article. Figure 2 ous concentrations of diamonds or other abrasive may be used but satisfactory results are obtained with 25% by volume of diamonds. I can make a satisfactory commercial article using as low as 61;% of diamonds by volume.

I then replace the mold in the hydraulic press and again press, this time with a pressure of the order of from v25 to 50 tons to the square inch. In this pressing operation, the height of the ring I diminishes to about one half. The diamond metal bond mixture I1 is compressed to about one over 2.5 times its original volume, as shown in Figure 3. The highly compressed ring |5a and i the'compressed abrasive portion I'Ia constitute an integral piece. I 4then take the metal ring |5a with the integral abrasive portion lla to" a sintering furnace and sinter at a temperature of around 600 C. (for the 20% tin, 80% copper mixture) for a period of two hours. This sinters the powders to form a homogeneous, integral article of great strength. For other metals and metal combinations, a satisfactory sintering temperature is one just below the melting point of the metal or of the final alloy. It will be noted that the temperature used for the copper-tin mixture is above the melting point of the tin although it is well below' the melting point of copper. This sintering should preferably be done in a reducing or neutral atmosphere. Y l The above-described sequence of steps is illustrative of those that I prefer to employ wherethe abrasive grains are metal-bonded and where the grinding wheel is to grind on an outer or peripheral face and hence where the stress imposed by the grinding action upon the ultimate support for the ring-like abrasive element is in a general radial direction; for an. illustrative and preferred sequence of steps to make up a ring-like abrasive element that has its abrasive portion on a different face,-such as a side face, and hence where the reaction from the grinding operation upon the center or support for the ring-like member is generally in the direction of the axis of the wheel, reference may be made to my abovementioned copending application, Serial No. 421,151.

I then machine the ring on that face or portion thereof at which it is to be attached to the center or support, and in this illustrative embodiment I hence machine the ring |5a on the inside face (the, outside face bearing the abrasive portion Ila as' above described) to give it a shape preferably as shown in Figures 4 and 5. As therein Y disclosed, the inside face or attaching portion of the ring has an inwardly projecting portion and an annular dovetailed portion 2|. There is thus provided on the inside of the ring I5a a pair of internal frusta-conical surfaces 22 and 23 whose elements in the preferred embodiments make angles of 20 degrees to the cylindrical periphery of the abrasive metal bonded grinding portion Ila. I'he annular dovetail 2|, in turn, has surfaces 24 and 25 which are external frustoconical surfaces the elements in the preferred embodiments of which make angles of 20 degrees toaradial plane bisecting the dove tail 2 I. 'I'hus the angle between surfaces 22 and 24 and between surfaces 22 and 25 is 90 degrees, although this angle may be varied. So also in each case the angle ofthe frusto-conical surfaces to the cylindrical periphery and the radial plane respectivelymayV vary preferably between 15 degrees and degrees. Within these limits the dove tail2l is very strong and'also when inter-engaged,

as fhereinafter described, with the moldabie and i curable resinoid mix to form the center or supf port, the change in volume, as by shrinkage, of the resinoid during curing coacts with these angles so that the shrinkage of the resin axially substantially balances the radial shrinking.

I then provide a mold, as shown in Figure 4. This mold may consist of an outer mold ring II),

a bottom plate 3|, a top plate l2, and a central arbor iitting in central holes I4 and 55, respectively, provided in the plates 3| and 32. From aV mixture of uncured resinoid and suitable filler such as asbestos, using a considerable amount of 'illler, for example, 40% by weight, I press a disk 36 having an axial hole I1 of the same size as the holes 34 and. I5. I place` this in the mold of Figure 4 inside of the ring I5a in the position shown. I then press with a pressure of the order of 4000 pounds to the square Inch which substantially closes the mold.' That is to say, the uncured resin flows under the dovetail 2| and` against the surfaces 22 and 24 and also over and into contact with the surfaces 23 and 25 and a small layer of it remains on` top of the ring Ii'a, which small layer can readily be trued ofi'.A I then remove the article from the mold and `cure it at resin curing temperatures.

phenol formaldehyde or anilineformaldehyde or any one of the alkyd resins or shellac or rubber or methyl methacrylate, styrene or other trans-y v parent resin material.

'I'he .curing temperature and time for phenol formaldehyde resin (having hexamethylene tetramlne hardening agent) is around one and one-half hours at C.

The ilnal article is shown in Figure 5 and comprises a cured center 16a, an annular metal portion or ring |5a having its attaching portion orface modified or shaped to provide or to comprise an annular dovetall 2| and an annular triangular portion 20 integral with the metal bonded diamond grinding portion I'Ia, the resinoid center 36a having a'central hole 31.

It might be thought that any interlocking arrelative to-the recesses in the metal part. The

use of an annular V shaped portionr2|l on the ring I5awhich is triangular' -in cross section in combination with an adjacent dovetail such as 2| gives a firm interlock with the resinoid into which they project and by which they are enveloped. During the heat treatment the resinoid shrinks and if merely cylindrical surfaces were provided in the ring Ila and on the center 36a, these parts would shrinkapart, leaving a space. VBut asthe resinoid shrinks inwardly In a radial direction, it also shrinks together in an axial direction and, therefore, moves down the surfaces 22 and 22 without separation. 'I'his action causes a firm pressure -to be exerted against the dovetail 2| which holds the parts rigidly interlocked. The portionsof the resinoid near thek surfaces 24 and 25 are under stress in the final article.

ny reference to Figure 5 it wm be seen that the vis on the other side of the just-mentioned horizontal plane. Also it will be noted that the anguiar recesses which theyform face in opposite directions, thus to receive more certainly the. two

portions of resinoid that are pressed into them by the stresses acting withinfthe resinoid during curing. These stresses act in efi'ect to substan The resin which I also refer to herein as "resinoid may be tially wedge or force each of the vtwo portions of the resinoid more tightly into its recess, for, as above stated, there is no detrimental separation between these resinoid portions and the surfaces 22 and 23. ,The above-mentioned firm pressure exerted against the dovetail 2| presses the portio'ns of the resinoid against the surfaces 24 and 25, these portions 'being'under stress as above stated and thus also nordetrmental separation takes place between them and their respectively engaged surfaces 2l and 25. The surfaces 22 and 23 form an angle whose apex is directed toward the axis of the wheel and the axially directed stresses in the resinoid caused during curing, move the two opposed portions of the resinoid toward each other and respectively against these inclined surfaces 22 and 23; a substantially similar action takes place with respect to the two inclined surfaces 24-25 which make an angle whose apex .is directed away from the axis of the vwheel. 'I'hus it will be seen that I am enabled to make use of forces or stresses created in the resinoid undergoing curing, for taking part in effecting a reliable junction of the resinoid with the attaching portion f the metal ring; these stresses or forces result primarily from change such as shrinkage in volume that the resinoid undergoes during curing.

Referring to Figure 6, a modification is illus-- trated comprising a center 35h, a metal annulus or base b and an abrasive portion llb which can be made by the method already described and which differs from the embodiment of Figures 1 to 5 onlyin omitting the annular dovetai-1 2|. This construction is found to be satisfactory for thick wheels, but for thin wheels the use of the dovetail is found to be preferable.

Its action in effecting a junction between the resinoid center or support and the metal ring will be understood from what is set forth above in connection with Figure 5, particularly with respect to the inclined surfaces and 23 of Figure 5, for in the modification of Figure 6 counterparts of those two surfaces 22-23 are employed and in the illustration they are extended to intersect, forming an angle whose apex is directed toward the axis of the wheel.

'I'he final article is of light weight because a large part of it consists of a resinoid center 36a, but the heat of grinding is conducted into a relatively large metal ring I5a which makes the wheel cool and free-cutting. The combination of the resinoid center, the metal ring, and the abrasive portion thus gives a light weight, cool-cutting grinding wheel. It will be noted that no diamond face or portion of the metal ring where there is no abrasive.

It will thus be seen that there has vbeen provided by this invention an article and a method in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As Various possible embodiments mightbe made of the mechanical features of the above invention and asthe art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. A peripheral abrasive wheel comprising a metal ring being, except for possible minor impurltles, all metal in a base part and metal bonded abrasive in a peripheral part, said two parts being integrally united and constituting a jointless unit, the base part having a pair of internal frusto-conical surfaces whose elements make angles of between fifteen and forty-five degrees with the peripheral surface, an annular dovetail constituting an integral part of the base part whose sides are external frusto-conical surfaces Whose elements make angles between fifteen and forty-five degrees with the radial plane bisecting the dovetail, and a center of cured organic material in contact with all of said frusto-conical surfaces and shrunk against them forming an integral article with no gap anywhere between the parts.

2. 'I'he method of making a grinding wheel comprising the steps of preforming a metal annulus having a rim of metal bonded abrasive grains and a central V-shaped annular portion projecting inwardly from a median plane of the annulus and thereafter pressing an uncured plastic resinoid body in position within said annulus and causing the resinoid to flow into full supporting contact with said V-shaped portion, and heating and curing the resinoid and thereby causing the curing shrinkage of the resinoid to provide a rigid and rm union between the resinoid body and the annulus supported thereby.

3. Method of making an abrasive wheel which comprises pressing a metal ring from metal powders under low pressure, placing said ring in a mold with an outer mold band slightly larger in its inside diameter than the outside diameter of said metal ring, lling the space between the metal ringand the mold band with a mixture of comminuted abrasive and metal powder, then pressing said ring axially and at the same time compressing said metal powder and metal abrasive under high pressure to form an integral article consisting of metal ring with an abrasive periphery, then sintering the article thus produced by heat, then machining the inside of the sintered ring to form an annular internal dovetail merging with a pair of internal frusto-conical portions formed on the ring, the elements of said frusto-conical portions making an angle between fifteen and forty-five degrees with a cylindrical surface coaxial with said ring, then pressing uncured organic material inside of said ring around said annular dovetail and into contact with said frusto-conical surfaces and curing said organic material to form an integral jointless body, the cured organic material being in stress adjacent the dovetail.

4. In a method of making an abrasive wheel that has a metal ring provided with an abrasive surface and an attaching portion, and a resinoid supporting member for said ring, the steps which comprise modifying the attaching portion of the metal ring to form at least two inclined surfaces for interaction with the resinoid material, lplacing the modified ring and an uncured resinoid mix in a mold with said inclined surfaces exposed to the resinoidl mix and with the angle subtended by said inclined surfaces extending in a direction.

related to Subsequent shrinkage of the mix to cause the portions of the mix respectively engaging said inclined surfaces to be forced toward each other and respectively against said inclined surfaces, pressing the mix relative to said supporting portion of the ring t iiow the mix into supporting contact with said inclined surfaces. and heating the mix to cure it and to cause the forces of shrinkage during curing of the mix to press the portions thereof respectively engaging said inclined surfaces thereagainst.

5. In a method of making an abrasive wheel that hasa metal ring provided with an abrasive surface and an attaching portion, and a resinoid supporting member for said ring, the steps which comprise, modifying the attaching portion of the metal ring to form at least two inclined surfaces making an angle whose apex is directed toward the axis of the wheel, placing the ring and an uncured resinoid mix in a mold with said inclined surfaces exposed to the resinoid mix so that respective portions of the mix engage said surfaces to be forced toward each other and respectively against said inclined surfaces by the forces exerted by subsequent shrinking of the resinoid in an axial direction, pressing the mix against said supporting portion of the ring to flow the mix into supporting contact with said inclined surfaces, and heating the mix to cure it and to cause the forces of shrinkage during curing of the mix to press the 'portions respectively engaging said inclined surfaces thereagainst to maintain tightness of engagement therewith.

6. In a method of making an abrasive wheel that has a metal ring provided with an abrasive surface and an attaching portion, and a resinoid supporting member for said ring, the steps which comprise, modifying the attaching portion of the metal ring to form at least two inclined surfaces making an angle whose apex is directed away from the axis of the wheel, placing the ring and an uncured resinoid mix in a mold with said inclined surfaces exposed to the resinoid mix so that respective portions of the mix engage said surfaces to be forced toward each other and respectively against said inclined surfaces by the forces exerted by subsequent `shrinking of the resinoid in an axial and radial direction, pressing the mix against said supporting portion of the ring to flow the mix into supporting contact with said inclined surfaces, and heating the l'mix to cure it and to cause the forces of shrinkage during curing of the mix to press the portions respectively engaging said inclined surfacesy there.

against to maintain tightness of engagement therewith.

7. In a method of making an abrasive wheel that has a metal ring that has an abrasive'surface and an attaching portion presenting a ringshaped face directed in a general direction toward the axis of the wheel, the steps which comprise modifying the said face to form thereon opposed axially spaced sets of re-entrant angu- I larly inclined surfaces, placing the modified ring and an uncured resinoid mix in a mold with the said modified face exposed to the mix and with said opposed re-entrant angularly inclined surfaces exposed to the mix so that subsequent shrinkage of the mix forces the resinoid into the opposed angularities to grip the intervening material of the ring, pressing the mix to .now the mix against said modified face and linto the angularities of said opposed sets of re-entrant angularly inclined surfaces, and heating to cure asado-4s the said mix and to causel shrinkage during curins of the latter to force the Aresinoid into said.

opposed ansulariues to enect mvpinsof the intervening portion of the ring.

8. An abrasive wh'eel comprising a metal ring 'having an abrasive portion and an attaching portion, and a resinoid supporting member for said ring, said attaching portion of the metal ring having thereon at least two inclined surfaces for interaction with the resinoid material portions of which are respectively engaged with said inclined surfaces, the angle subtended by said inclined surfaces extending in a direction relative to the direction of shrinkage of the resinoid of said supporting member during curing to make the forces resulting from shrinkage press said portions respectively engaging said inclined surfaces lthereagainst.

9. An abrasive wheel as claimed in claim 8 in which the inclined surfaces are positioned relative to each other and to the axis of the ring so that the apex of said angle is directed toward the axis of the wheel, whereby shrinkage in an axial direction during curing in eii'ect draws said two portions of the resinoid vmaterial toward each other to e maintain tightness of engagement thereof with their respectively engaged inclined surfaces.. I

10. A grinding wheel as claimed in claimr 8 in which said inclined surfaces are positioned-relative to each other and to the axis of said ring so that the apex of said angle subtended thereby is directed away from the said axis, whereby shrinkage in both radial and axial directions of the resinoid material during curing effects tightness of engagement of said -resinoid portions with their respectively engaged inclined surfaces.

1i. An abrasive wheel comprising a metal vring having an abrasive portion and an attaching portion, and a resinoid supporting member for said ring, said attaching portion extending in the genvrespectively with said sets of re-entrant inclined surfaces and are in engagement with the latter,

l the inclinations of said surfaces and the respective angularities formed -by each of said sets being in respective. directions relative toy axial shrinkage during curing of the material of the resinoid of said supporting member to make the forces resulting from shrinkage press portions of the resinoid supporting member respectively into;

said angularities to effect-a gripping therebetween of the intervening portions of said metal ring and to effect tightness ofengagement of portions of the resinoid of said supoprting member with their respectively engaged inclined surfaces.

12. An abrasive wheel comprising a metal ring Vhaving an abrasive portion and an attaching portion, anda resinoid supporting member for said ring, said attaching portion oi' the metal ring having at least two are at an angle to each other and formlf-'therebetween an `open annular space which, because of `the angle between said surfaces,'is of substantially tapering cross-section, said resinoid supporting member having annular portions ofv the resinoid thereof entered into said space and respectively engaged with said two surfaces, thesaid surfaces being positioned relative to the direction of'stresses caused in the resinoid of said supporting member by and during curing of the resinoid thereof to make said stresses press said annular portions of the resinoid into said space of tapering crosssection to effect gripping engagement of said annular resinoid portions respectively against said two surfaces, the cured resinocl material being in stress in the portions thereof engaging said two surfaces.

13. In a method of making an abrasive wheel that has metal ring provided with an abrasive surface and an attaching portion, and a resinoid supporting member for said ring, the steps which comprise modifying the attaching portion of the metal ring to form thereon at least two surfaces that are at an angle to each other to form an open annular space which, because of the angle between said surfaces, is of substantially tapering cross-section, placing the modified ring and an uncured resinoid mix in a mold with said surfaces and said open annular space exposed to the resinoid mix in a direction related to the stresses caused in the resinoid by and during subsequent curing thereof to make said stresses press the resinoid into said space of tapering cross-section and against said surfaces, pressing the uncured resinoid mix to ow the mix into full supporting contact with said two surfaces and into said space of tapering cross-section, and heating the mix to cure it and to cause the said stresses in the curing resinoid to press annular portions of the resinoid progressively into said space of ta paring cross-section to effect gripping engagement of said annular resinoid portions, respectively, against said two surfaces.

EDWARD VAN DER PYL. 

